The present invention is a further developed engine system based on the cold-expansion concept in the eight-stroke-cycle used in an eight-stroke-engine, which is now U.S. Pat. No. 6,918,358; the theory of the eight-stroke-cycle is to reduce the heat dissipation by way of releasing the fuel energy in two processes, thereby shortening the time that the combustion-medium is heating the cylinder wall and the cylinder head, so a better fraction of the fuel energy is conversed in a low-temperature oxygen-rich cold-expansion-medium for producing power with the least heat-loss.
The abovementioned two processes are the hot-combustion-process and the cold-expansion-process; the hot-combustion-process will combust the fuel and the air at a high temperature (about 2500 degree Celsius to 1700 degree Celsius) as a hot-combustion-medium, the hot-combustion-medium consists of nitrogen-gas, carbon-monoxide-gas, and other hot gases (except carbon-dioxide-gas due to the environment condition); the second-intake-process will mix a controlled amount of pressurized air with the hot-combustion-medium, thereby blocking the heat-loss by an instant cooling effect that rapidly cools the average temperature of the hot-combustion-medium down by 30%-80%, thereafter forming a low-temperature oxygen-rich cold-expansion-medium at a precisely regulated temperature range (400-1100 degree Celsius) according to the engine load; next the cold-expansion-medium expands with almost no heat-loss since the temperature difference between the cold-expansion-medium and the cylinder wall is now reduced significantly, which stops the heat current from conducting throughout the cylinder wall into the cooling circulation of the engine, and the conversion of the carbon-dioxide-gas is accelerated due to high oxygen-gas concentration presented in the cold-expansion-medium; therefore, almost all the carbon-monoxide-gas is converted into the carbon-dioxide-gas before the up-stroke of the piston, which yields an very high average expansion pressure during the down-stroke of the piston with virtually 50% the heat-loss of the conventional engine, in other words, the eight-stroke-cycle allows the fuel energy to be released in two distinctive steps (the hot-combustion-process and the cold-expansion-process), instead of the sudden and complete energy release that occurs in the conventional engine.
In a regular (medium load) operation with the optimal efficiency of the eight-stroke-cycle, the cold-expansion-medium is expanding at an average medium temperature about 850-600 degree Celsius during the cold-expansion-process, the heat current conducing throughout the cylinder wall is significantly lower than that of the convention engine (gasoline type), whereas the exhaust-gas of the conventional engine has an average temperature of about 1500 degree Celsius or higher during the power-stroke, and an average temperature of about 1400 degree Celsius during the exhaust-stroke.
As the heat current is directly proportional to the temperature difference between the combusting medium and cylinder wall, it can be seen that the total heat-current conducted over time (or the heat-loss) of the eight-stroke-engine is roughly about half of that of the conventional engine; therefore the eight-stroke-cycle is capable of performing at a relatively higher energy efficiency and power-to-weight ratio than the conventional engine.
And a secondary advantage is that, the eight-stroke-engine requires a cooling-system about half of that of the conventional engine, which also reduces the weight of the entire engine system.
However, there is a few drawbacks on the eight-stroke-engine, one of which is the high cost of the variable crankshaft control system of the slave-cylinder of the eight-stroke-engine and the variable-timing-coordinate-valve-system that makes it difficult for the eight-stroke-engine to adapt to the automobile applications.
As the automobile applications require a demanding power-responsive performance that can almost instantly accelerate from 10% of the maximum engine load to 100% of the maximum engine load in about 3 or 4 seconds.
After experimenting on improving the eight-stroke-engine for years, my research team develops a more advanced engine system named Mackay Cold-Expansion Engine System based on the operation concept of the eight-stroke-engine.
Mackay Cold-Expansion Cycle takes in the idea of the two combustion processes of the eight-stroke cycle, and further controls the expansion temperature and increases the power-to-weight ratio with the fuel-cooling-process, wherein the hot-combusting-medium is cooled down with the vaporization of the fuel before the second-intake-process is initiated; and more importantly, Mackay Cold-Expansion Cycle can now respond to a change in engine load much faster and smoother than the eight-stroke-engine by a systematic control means.
Mackay Cold-Expansion Engine System (MCES) consists of an air-compression means, an air-buffer-system, at least two cold-expansion-chambers, and a power management unit; wherein each cold-expansion-chamber will operate in a Mackay Cold-Expansion Cycle consisting of the first-intake-process, the hot-combustion-process, the fuel-cooling-process, the second-intake-process, the cold-expansion-process, and the active-exhaust-process (or the exhaust-process).
Mackay Cold-Expansion Engine System may also operate each cold-expansion-chamber in a Simplified Mackay Cold-Expansion Cycle, in which the fuel-cooling-process is disabled, such that each cold-expansion-chamber will operate in a Simplified Mackay Cold-Expansion Cycle consisting of the first-intake-process, the hot-combustion-process, the second-intake-process, the cold-expansion-process, and the active-exhaust-process (or the exhaust-process).
In comparison with the conventional engine, the MCES will have a relatively higher average expansion pressure and a relatively lower average expansion temperature during the entire down-stroke of the piston; therefore the heat energy dissipated in the engine cooling system of the MCES is only about 7%-15% of the total fuel energy, whereas the conventional engine dissipates about 35% of the total fuel energy in the engine cooling system.
For the ease of comprehension, a MCES and a conventional engine of the equivalent power output are compared as follows in their respective medium load operations at their standard energy efficiencies:
The hot-combustion-medium of the MCES will be heating the chamber wall at an average temperature about 1600-2000 degree Celsius during the hot-combustion-process (a duration of about 45 degree crankshaft rotation), and then heating the chamber wall at an average temperature about 500-800 degree Celsius from the second-intake-process to the active-exhaust-process (a total duration of about 270 degree crankshaft rotation).
Whereas the working-medium of the conventional engine (4-stroke spark-ignition) will be heating the chamber wall at an average temperature about 1500-2000 degree Celsius during its combustion process (a duration of about 160 degree crankshaft rotation), and then heating the chamber wall at an average temperature about 1200-1400 degree during its exhaust-process (a duration of about 180 degree crankshaft rotation.
As the heat-loss of the MCES is significantly less than the conventional engine, this converts more a better fraction of the fuel energy into expansion force, to be more detailed, the airflow-volume and the exhaust pressure measured at the exhaust-means of the MCES are also relatively higher than the conventional engine, which induces the MCES to recover the energy of the cold-expansion-medium from a different approach, therefore, a heat-energy-recovering means (the heat-transfer-catalytic-converter) and a kinetic-energy-recovering means (the turbo-turbine and the turbo-compressor) are integrated into the MCES to maximize the overall energy efficiency.
Due to the low temperature characteristic of the expelled cold-expansion-medium, the most widely used steam-heat-recovery-systems nowadays which utilizes the exhaust-gas to generate a high pressure steam to drive turbine for electricity is not suitable for collaborating with the MCES; this is because the general steam-heat-recovery-system requires the exhaust-gas to be at least 600 degree Celsius or higher to be economically efficient in terms of the equipment cost, whereas the temperature of the exhaust gas from a Mackay Cold-Expansion Engine System is only about 300-400 degree Celsius in the regular operation; therefore, a configuration of the MCES consisting of the refrigerant-regenerator is also provided in the disclosed embodiments for the power generation purpose.
Various configurations and design concepts of Mackay Cold-Expansion Engine System are provided herein to the best of the applicants' knowledge, so that those skilled in the art of the power generation can maximize the potential of the Mackay Cold-Expansion Cycle according to the operation environments, and it is the earnest wish of my research team to provide an efficient engine system that can contribute to alleviate the ongoing energy crisis.